1. Field of the Invention
This invention relates to a pressure gauge for a pneumatic tire, more particularly to a pressure gauge having an energy-saving switch assembly for a pressure responsive signal-generating device.
2. Description of the Related Art
U.S. Pat. No. 5,694,111 teaches a pressure gauge of a tire pressure indicator for a set of pneumatic tires, the entire disclosure of which is incorporated herein by reference. The pressure gauge comprises a casing and a pressure responsive signal-generating device disposed in the casing. A power source is connected electrically to the signal-generating device for supplying the electric power required by the signal-generating device. Since the signal-generating device is activated constantly by the power source that includes two lithium button cells or two mercury button cells connected in series, the power will be used up quickly.